Biocomposites sheet molding and methods of making those

• US 20060046042A1
• Filed: 10/15/2004
• Published: 03/02/2006
• Est. Priority Date: 10/15/2003
• Status: Active Grant

• Current Assignee: The Board of Trustees of Michigan State University (Michigan State University)
• Original Assignee: The Board of Trustees of Michigan State University (Michigan State University)
• Inventors: Drzal, Lawrence T., Mohanty, Amar K., Thayer, Kelby, Mehta, Geeta, Misra, Manjusri
• Granted Patent: US 7,208,221 B2
• Time in Patent Office: Days
• US Class Current: 428/292.100
• CPC Class Codes: B29C 70/504 using rollers or pressure bands for corrugating B29C53/22
• CPC Class Codes: B29C 70/506 and impregnating by melting a solid material, e.g. sheet, powder, fibres B29C70/508 takes precedence
• CPC Class Codes: B29K 2067/06 Unsaturated polyesters
• CPC Class Codes: B29K 2311/10 Natural fibres, e.g. wool or cotton
• CPC Class Codes: B29K 2709/08 Glass
• CPC Class Codes: D04H 1/425 Cellulose series
• CPC Class Codes: D04H 1/4266 Natural fibres not provided for in group D04H1/425
• CPC Class Codes: D04H 1/558 in combination with mechanical or physical treatments other than embossing
• CPC Class Codes: D04H 1/587 characterised by the bonding agents used
• CPC Class Codes: D04H 1/74 the fibres being orientated, e.g. in parallel (anisotropic fleeces)
• CPC Class Codes: Y10T 428/249924 Noninterengaged fiber-containing paper-free web or sheet which is not of specified porosity
• CPC Class Codes: Y10T 428/24994 Fiber embedded in or on the surface of a polymeric matrix
• CPC Class Codes: Y10T 428/24995 Two or more layers
• CPC Class Codes: Y10T 442/675 Ester condensation polymer sheet or film [e.g., polyethylene terephthalate, etc.]

Abstract

A Sheet Molding Compound (SMC) as prepregs and cured compositions with naturally derived fibers which have been dried for at least three hours is described. The SMC process combines polyester polymer or resin with the fibers preferably continuously. The molded products are useful for a variety a purposes where glass fiber filled polyester polymers are conventionally used.

Claims

1. A prepreg which comprises:

(a) a dried mat of naturally derived fibers with a moisture content of less than 10%; and

(b) a matrix comprising a gelled polyester resin which has been catalyzed to form cured polyester resin intermixed with the fibers, wherein the prepreg is stored at refrigeration temperatures prior to a heat and compression curing of the prepreg.

3. The composition of claim 1 wherein the prepreg has a shelf life prior to the forming of the prepreg of at least one day.

4. The composition of claim 1 or 2 wherein the polyester resin has been gelled during the refrigeration.

5. The composition of claim 1 or 2 wherein the fibers have been chemically modified to enable reaction with the polyester resin.

6. The composition of claim 1 or 2 wherein the fibers have been treated with a compatibilizer which enables intermixing of the fibers with the polyester resin at least during curing.

7. The prepreg of claim 1 or 2 wherein the fibers are chopped.

8. The prepreg of claim 1 wherein the fibers are as a woven or non-woven as a mat.

9. The prepreg of claim 1 wherein the fibers are chopped and have a length ranging between 1 mm and 50 mm.

10. The prepreg of claim 1 wherein the fibers are either randomly oriented or preferentially aligned in one direction.

11. The prepreg of claim 1 wherein the natural fibers are combined with other fibers either within the mat, or with other mats of a different fiber composition.

24. A heat and pressure cured formed object prepreg as in claim 1.

2. A sheet forming prepreg which comprises:

(a) a first carrier film;

(b) a dried mat of naturally derived fibers with a moisture content of less than 10%;

(c) a matrix comprising a gelled polyester resin which has been catalyzed to form a cured polyester resin intermixed with the fibers; and

(d) a second carrier film with the mixture of the matrix paste and fibers between the first and second fibers, wherein the prepreg is stored at refrigeration temperatures prior to a heat and compression curing of the prepreg.

12. A process for forming a prepreg which comprises:

(a) intermixing a matrix comprising a polyester resin which has been catalyzed to form a cured polyester resin with a dried mat of naturally derived fibers with a moisture content of less than 10%;

(b) storing the prepreg at refrigeration temperatures prior to curing of the prepreg.

14. The process of claim 12 or 13 wherein the prepreg has a shelf life prior to the curing of the prepreg of at least one day.

15. The process of claim 12 or 13 wherein the polyester resin is gelled during the refrigeration.

16. The process of claim 12 or 13 wherein the fibers have been chemically modified to enable reaction with the polyester resin.

17. The process of claim 12 or 13 wherein the fibers have been treated with a compatibilizer which enables intermixing with the polyester resin at least during curing of the prepreg.

18. The process of claim 12 or 13 wherein surfaces of the fiber have been chemically modified to react with the polyester resin at least during curing.

19. The process of claim 12 or 13 wherein the fibers are chopped.

20. The process of claim 12 or 13 wherein the fibers are chopped and have a length ranging between 1 mm and 50 mm.

21. The process of claim 12 or 13 wherein the fibers are either randomly oriented or preferentially aligned in one direction.

22. The process of claim 12 or 13 wherein the natural fibers are combined with other fibers either within the mat, or with other mats of different fiber composition.

23. The process of claim 12 or 13 wherein the fibers have been woven or are non-woven as the mat.

25. The process of claim 12 or 13 wherein the prepreg is in addition formed and cured into a formed object.

13. In a process for forming a cured sheet the improvement which comprises forming a prepreg which comprises:

(a) providing a first carrier film;

(b) providing a dried mat of naturally derived fibers with a moisture content of less than 10%;

(c) intermixing a matrix comprising a gelled polyester resin which has been catalyzed to form a cured polyester resin with the fibers; and

(d) providing a second carrier film with the mixture of the matrix paste and fibers between the first and second fibers;

(e) storing the prepreg at refrigeration temperatures prior to heat and compression curing of the prepreg.

26. An apparatus for describing chopped fibers continuously as a mat on a conveyor surface which comprises:

(a) a hopper with a screw feeder for delivering the chopped fibers to an outlet;

(b) an inclined fiber distribution feed chute at the outlet of the hopper with a series of rods on the chute which laterally disperse a portion of the fibers along with a shaking means mounted on the chute which vibrates the chute to move the fibers down the incline and off the incline; and

(c) a vibratory feeder with a tray below the chute for receiving the fibers from the chute, wherein the fibers are deposited as a mat on the tray and are dispersed from the tray by a slot in the tray allowing the mat as it advances on the tray of the feeder to be deposited onto the conveyor surface.

27. The apparatus of claim 26 wherein the shaking means for the chute is provided by the vibratory feeder.

28. The apparatus of claim 26 wherein an independent shaking means is mounted on the chute.

29. The apparatus of any one of claim 26, 27 or 28 which in addition includes the conveyor and a production line for forming a sheet molding compound.